ANATOMY FOK NUKSES. 



[CHAP. I. 



while the limbs are solid or semi-solid, contain no viscera, and 

 are merely appendages of the trunk. The limbs or extremities, 

 upper and lower, are in pairs, and bear a rough resemblance to 

 one another, the shape of the bones, and the disposition of the 

 muscles in the thigh and arm, leg and forearm, ankle and wrist, 

 foot and hand, being very similar. 



The trunk and head contain two main cavities, and looking 

 at the body from the outside we should naturally imagine that 

 these two cavities were the cavity of the 

 head and the cavity of the trunk, respec- 

 tively. If, however, we divide the trunk 

 and head lengthwise into two halves, by 

 cutting them through the middle line 

 from before backwards, we find the trunk 

 and head are divided by the bones of the 

 spine into back and front cavities, and 

 not into upper and lower (vide diagram). 

 The dorsal or back cavity is a com- 

 plete bony cavity, and is formed by the 

 vertebrae (bones of the spine) and of the 

 bones of the skull. It may be subdi- 

 vided into the spinal canal, containing 

 the spinal cord, and into the cranial cav- 

 ity, which is merely an enlargement of 

 the spinal canal, and contains the brain. 

 Connected with the dorsal cavity are the 

 FIG. i. DIAGRAMMATIC two small orbital cavities containing the 



LONGITUDINAL SECTION OF f { } t 

 THE TRUNK AND HEAD. 1,1, & 



the dorsal cavity; a, the The ventral or front cavity is not a 

 'omplete bony cavity, part of its walls 



bodies of the vertebrae form- being formed of muscular and other tis- 



in- the partition between ... ,111 



the dorsal and ventral cavi- sue 5 ^ ^ much larger than the dorsal 



ties; 2, 2, the ventral cavity, cav it y , and may be subdivided into the 



subdivided into thoracic cav- *\ , , . , , , . 



ity (d), abdominal cavity thoracic, abdominal, and pelvic cavities. 



(e) and pelvic cavity (/); Th thoracic cav ity, or chest, contains the 



y, the nasal cavity; h, the J 



month, or bnccai cavity, trachea or windpipe, the lungs, gullet, 



heart, and the great vessels springing 

 the whole length of the ven- from, and entering into, the heart. The 



abdominal cavity contains the stomach, 

 liver, gall-bladder, pancreas, spleen, kidneys, small and large 



